•§> 121. THE TURBELLARIA. 133 



Genera : Polycelis, Monocelis, Planaria, Leptoplana, Eurylepta, Planoce- 



ra, Thysanozoon. 



BIBLIOGRAPHY. 



Baer. Ueber Planarien, in the Nov. Act. Acad. Leop. XIII. 1826, 

 p. 691. 



Dugh. Recherches sur I'organisation et les moeurs des Planariees, in 

 the Ann. d. Sc. Nat. XY. 1828, p. 139; and XXL 1830, p. 72. See 

 Isis 1830, p. 169, or Froriep's, Not. 1829, No. 501. 



Mertovs. Ueber den Bau verschiedener in der See lebender Planarien, 

 in the Mem. de I'Acad. de St. Petersbourg, 6'='"^ Ser. Tom. II. 1833, p. 1. 



Ehrenberg. Phytozoa turbellaria, in the Symbolae physicae, Ser. I. 

 1831. 



Focke. Ueber Planaria Ehrenbergii. in the Ann. des Wiener Mus. I. 

 Abth. 2, 1836, p. 193. 



F. F. Schulze. De Planariarum vivendi ratione et structura penitiori 

 nonnuUa. _ Dissertatio. Berolini, 1836. 



A. S. Orsted. Entwurf einer systematischen Eintheilung und speciel- 

 len Beschreibung der Plattwiirmer. Copenhagen, 1844. 



ADDITIONAL BIBLIOGRAPHY. 



Beside the writings referred to in my notes, see the following : 



Schmidt. Die rhabdocoelen Strudelwiirmer des siissen Wassers. Jena, 

 1848. 



Neue Beitriige zur Naturgesch. der Wiirmer. Jena, 1848. Erster 

 Abschnitt, Turbellarien. 



Handbuch d. vergleich. Anatomic, 1849, p. 294. 



M. S. Schultze. Ueber die Microstomeen, eine Familie der Turbellarian, 

 in Wiegmann's Arch. 1849, p. 280, Taf. VI. 



Beitrage zur Naturgeschichte der Turbellarien. 1851. — Ed. 



CHAPTER I 



CUTANECWS SYSTEM. 



§121. 



The whole body of the Turbellaria is covered with ciliated epithelium, 

 under which lies a loose cellular parenchyma. In this parenchyma, and 

 directly beneath the epithelium, there are found, in many species, particu- 

 lar cell-like bodies, which sometimes remind one of the nettling organs of 

 certain zoophytes, and sometimes exactly resemble the prehensile organs 



12 



